What is the difference between UPF and SPF?

UPF (Ultraviolet Protection Factor) and SPF (Sun Protection Factor) are two measurements used to designate the level of sun protection in clothing and sunscreen, respectively. While SPF indicates the level of protection against UVB radiation, which primarily causes sunburns, UPF measures the amount of UVA and UVB radiation blocked by fabric. SPF rating only applies to sunscreens, whereas UPF is specific to fabrics. An SPF of 30, for instance, implies that it will take 30 times longer for the skin to burn compared to when no sunscreen is used. Conversely, a UPF of 50 means that only 1/50th (or 2%) of the UV rays will penetrate the fabric. Both factors are essential in safeguarding against harmful sun exposure, with UPF being significant for clothing while SPF is important for sunscreens.